Curofy
Sushmita Haodijam (MBBS Student) needs a second opinion on this medical case.
Respiratory Failure
Definition: Clinically respiratory failure is defined as PaO2 <60 mmHg while breathing air, or a PaCO2 >50 mmHg.
Type 1 respiratory failure - low PaO2 & low or normal PaCO2.
-Type 2 respiratory failure -low PaO2 & raised PaCO2
_TYPES OF RF:_
1. Acute hypoxia without hypercapnia - acute type 1.
2. Chronic hypoxia without hypercapnia - chronic type 1.
3. Acute hypoxia with hypercapnia - acute type 2.
4. Chronic hypoxia with hypercapnia -chronic type 2.
Clinical Features:
-Cyanosis
-Unoxygenated hemoglobin 50 mg/L
-Dyspnea: secondary to hypercapnia and hypoxemia
-Paradoxical breathing
-Confusion, somnolence and coma
-Convulsions
-Circulatory changes: tachycardia, hypertension, hypotension
-Polycythemia: chronic hypoxemia-erythropoietin synthesis
-Pulmonary hypertension: Cor-pulmonale or right ventricular failure.
ACUTE TYPE 1 RF:
_Causes_:
-pneumonia.
-pulmonary edema.
-acute respiratory distress syndrome.
-pulmonary embolism.
- pneumothorax.
_Management:_
-Treat underlying condition.
-High conc of oxygen.
-Artificial ventilation.
CHRONIC TYPE 1 FAILURE:
_Causes:_
-diseases associated with pulmonary fibrosis.
-chronic chest wall or neuromuscular diseases.
-chronic pulmomary edema pulmonary thromboembolism.
_Management:_
-Treat underlying cause.
-Oxygen therapy.
-Artificial ventilation.
-Venesection to reduce haematocrit for polycythemic.
-Diuretics to reduce peripheral edema.
ACUTE TYPE 2 RF:
-Causes:_
-depressant drugs like diazepam, opiates & alcohol.
-brainstem damage from stroke & trauma.
-disorders of nerves & neuromuscular transmission like GBS.
-Disorders of muscles like acute polymyositis.
-severe airflow obstruction.
-chest injuries resulting in tension pneumothorax-flial chest.
_Management:_
-treat underlying condition.
-oxygen therapy 24% oxygen.
-removal of secretions by coughing or emergency bronchoscopic aspirations.
-bronchodilators.
-assisted ventilation.
CHRONIC TYPE 2 PF:
_Causes:_
-COPD.
-Chestwall abnormalities like gross kyphoscoliosis.
-central hypoventilation.
_Management:_
-treat underlying cause.
-oxygen therapy carries the risk of rise in PaCO2 resulting in confusion, drowsiness.
-measure ABG levels before oxygen therapy.
-do not give more than 24% oxygen.
-give oxygen continously not intermittently at a rate of 1-2 litre/min.
-stimulant drugs advocated like doxapram hydrochloride.
-mechanical ventilation reserved for non respondant.
-supportive treat includes antibiotics, nebulisers,clearing secretions by coughing, suction.
Mechanical Ventilation (MV):
-Non invasive with a mask.
-Invasive with an endobronchial tube.
-MV can be volume or pressure cycled -For hypercapnia:
•MV increases alveolar ventilation and lowers PaCO2, corrects pH.
•Rests fatigues respiratory muscles.
-For hypoxemia:
•O2 therapy alone does not correct hypoxemia caused by shunt.
•Most common cause of shunt is fluid filled or collapsed alveoli (Pulmonary edema).
Positive End Expiratory Pressure:
-PEEP increases the end expiratory lung volume (FRC).
-PEEP recruits collapsed alveoli and prevents recollapse.
-FRC increases, therefore lung becomes more compliant.
-Reversal of atelectasis diminishes intrapulmonary shunt.
-Excessive PEEP has adverse effects
•decreased cardiac output
•barotrauma (pneumothorax, pneumomediastinum)
•increased physiologic dead space
•increased work of breathing